BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention will be described in greater detail on the basis of the illustrated embodiment shown in schematic manner in the figures. There is shown
FIG. 1 a motor vehicle with a sensor device integrated into the bumper for detection of an impact with a pedestrian, in perspective representation;
FIG. 2 a vertical cross-section segment of FIG. 1;
FIG. 3 the sensor device in cut-away longitudinal section;
FIG. 4 a section along section line 4-4 in FIG. 3;
FIG. 5 a signal trace of an impact signal detected by the sensor device;
FIGS. 6 & 7 further embodiments of a carrier body for the sensor device in a representation corresponding to FIG. 4; and
FIG. 8 a sensor device with a number of sensor lines in a schematic representation.
DETAILED DESCRIPTION OF THE INVENTION
The sensor device 10 shown in the figures can be employed in general for detection of an external impact load on a vehicle 12 and serves in particular for detection of a pedestrian impact. The sensor device includes for this purpose a sensor line 14, a longitudinally extending carrier body 16 for receiving the sensor line, a deformation structure 18 contained in the carrier body and a measuring unit 20 cooperating with the sensor line for providing a measurement signal or, as the case may be, impact signal.
As can be seen particularly from FIGS. 3 and 4, the deformation structure 24 includes two comb-like partial pieces 22, 24 which are limitedly movable relative to each other upon application of an external force thereby causing local bending of the linear sensor line 14. The bending exposure is actualized by force transmission elements 26 engaging sideways on the sensor line 14, which are provided distributed irregularly along the length of the sensor line. By a corresponding variation of the spacing relative to each other of these adaptation means, the force transmission can be locally adapted to the solidity or yield strength of the surrounding vehicle part, so that in the case of a given external force the degree of deformation remains the same independent of where the point of impact is located.
The sensor line 14 is comprised of a light guide or, as the case may be, an optical fiber cable, which includes two parallel to each other running fiber segments connected at an end, not shown in FIG. 3, for example by a loop so as to be continuous. The light entry and light emission ends are coupled with the opto-electronic measuring unit 20. Evaluation software can also be loaded into the measuring unit 20, so that no separate control device is necessary. The total device is sealed cast into a receptacle casing 28 and can thus be simply integrated into the vehicle 12. It is also possible that the sensor line 14 includes additional not shown optical fibers, which are employed for example for reference measurement.
In the installation arrangement shown in FIG. 1 and 2 the sensor line 14 runs along the front bumper 30 of the vehicle 12, wherein the carrier body 16 is enclosed between a front absorber body 32 and a rear transverse carrier 34. It is also conceivable to install the sensor device 10 in a hollow space of a side door 36, in order to detect a side impact. Another application of the device could comprise detecting a pinning or clamping (of, e.g., a limb) in the area of an electrically operated side window or in the area of the retractable or sliding roof.
Upon application of external pressure or, as the case may be, the action of an impact, the optical fiber 14 is bent at the respective impact location in corrugated manner by the transmission elements 26 of the deformation structure 18, so that the sensing light passing therethrough changes in intensity or, as the case may be, experiences and attenuation. As shown in FIG. 5, this results, in correspondence with the size of the instantaneous deformation, in a (negative) signal peak 38 in the signal trace. The amplitude thereof serves as the gage or measure of the impact strength. Thereby, as a result of the design of the deformation structure 18 in adaptation to the environment of installation, an absolute evaluation is possible.
It is possible in all embodiments to use the signal trace 40 outside of the signal peak 38 for the continuous self-diagnosis of the sensor device 10. In this long time range a system-dependent dampening component occurs, which causes a drift shown in exaggerated form in FIG. 5, depending upon temperature, preload and other assembly or configuration perimeters. While the dynamic signals 38 occur in a fraction of a second, the time scale of the signal drift is substantially higher than this. The slowly changing signal level is compared with a predetermined threshold value 42, which if exceeded is diagnosed as a sensor malfunction. Therein it is advantageous when the threshold value 42 is so selected, depending upon the maximum dynamic signal to be detected, that it is always possible fundamentally to detect the full peak amplitude. It is not necessary that the threshold value be maintained constant therein, but rather it can be updated for example depending upon operating and environment parameters.
In an alternative embodiment it is envisioned that the carrier body directly or intimately surrounds the optical fiber line or, as the case may be, light guide 14, and upon mechanical deformation influences the refractive index and therewith the transmission or as the case may be attenuation of the light signal in the optical fiber line.
The illustrated embodiments shown in FIGS. 6 and 7 differ from the embodiment according to FIG. 3 and 4 in that the force transmission elements 26 engaging comb-like in each other are provided spaced evenly apart, while the sideways connecting walls 44, 46 act on the deformation bodies 22, 24 as elastic spacers with a stiffness that is modified where required. In this manner the force transmission can be adjusted variably along the light guide 14. According to FIG. 6 the beveled wall 48 acts herein as a leaf spring, in order to adapt to the area being measured. In FIG. 7 for this purpose the sidewalls 46 connected to the adhesion location 50 are sideways elastically bendable. In both cases only one guide segment 14′ is subjected to the deformation, in comparison to which the segment 14″ led back via a loop remains undeformed, for example in a foamed grout mass 52.
For localized detection multiple parallel running light cables 14 can be provided as conductor or guide row (L1-L5) as seen in FIG. 8, wherein the elements of the row are sectionally in engagement with the deformation structure 18 forming work segments 54, and therefrom non-sensitive blind segments, for example covered by a not shown covering. In order to make the position recognition more precise, the active segments of respectively two row elements (L1, L2; L2, L3 . . . ) are in a length ratio of 2:1. Accordingly, in the distribution or arrangement shown in FIG. 8 the force influence can be recognized for example in the area of the longitudinal segment 58 by a simultaneous signal from lines L1, L3 and L4 with the absence of signals in the remaining lines.
For detecting a pedestrian impact the sensor line or as the case may be light guide or conductor bundle should run as far forward on the vehicle as possible, in order to detect the impact as early as possible. Besides this, a low force level must be detectable, in order to be able to distinguish a collision with a pedestrian in comparison to a hard impact with a solid object. The sensor device can also be employed in order to relay the early impact detection signal to safety devices such as air bags or crash boxes. In particular, it is also possible to so adjust or program the crash box that they are adjusted to be soft in the case of a pedestrian impact and harder in a different type of impact. Thereby a soft setting should be selected as preset, in order to give priority to protecting the pedestrian.
Patent Application
20080060450
